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Top 10 mechanical ventilation installation mistakes

The majority of complaints that Titon Engineers are called out to site to resolve are the result of installation or commissioning mistakes or the product being damaged by mishandling which are counter chargeable. Here Titon sets set out the most common mistakes that lead to complaints.

1. Not using or following a professional system design (poor performance, excessive noise)

Ventilation Systems must be professionally designed to ensure they meet the required performance standards and work quietly and efficiently. The system designer should provide detailed drawings showing the layout, all product selections and the design performance characteristics. Any variation from the design provided must be approved by the system designer to ensure performance is not adversely affected. If you choose to not to use a professional design or to vary from a design provided you may be held responsible for any subsequent performance issues.

2. Excessive use of flexible ducting (poor performance, excessive noise)

Even when it is installed properly, flexible ducting has a much greater resistance to airflow than smooth bore rigid ducting and its use must be avoided where possible. Where it is used, for example, to connect the MVHR unit to the solid ducting to allow for slight differences in alignment. We recommend it should only be used in short straight lengths pulled taut to a maximum length of 300mm.

3. Not adequately sealing or supporting ducts (poor performance, excessive noise)

All duct joints must be made airtight and properly sealed by either using a proprietary fitting with an integral rubber seal or by applying a suitable non-hardening sealant. Duct tape alone is not suitable and will not provide a long-term seal. Ducting should be supported to ensure it will remain intact and not cause joint stress.

4. Using the wrong type of terminals (poor performance, excessive noise)

There are many products sold as ventilation terminals that are totally unsuitable for systems ventilation as they will strangle airflow or allow water ingress. Only use the terminals detailed by the System Designer that have been chosen because they meet specific performance standards for use with continuously running mechanical ventilation systems. Terminals fitted with an insect guard, ridge ventilation terminals, SVP or flue terminals are normally unsuitable.

5. Not insulating ducting (excess moisture, water leaks)

When warm air comes in to contact with a cold surface it produces moisture. Moisture may form on the inside or the outside of a duct and may collect in the ducting system and unit or damage surroundings. All ducting and duct accessories connected to the outside air, or running outside the heated space, must be continuously insulated and the insulation must have a vapour barrier to prevent it from absorbing the moisture. Any vertical ducting carrying the extracted air to the outside may also require an additional inline condensation trap. The smallest of gaps in the insulation can result in water damage.

6. Wiring a ventilation unit incorrectly (unit not running, not responding to controls)

Your product may use zero or low voltage switching circuits and accessories that can be easily damaged by the application of high (mains) voltage or can be affected by induced power when running cables together with higher voltages. Always ensure the product handbook instructions have been followed before making any connections.

7. Not installing user controls or adjusting humidity or timer settings (excessive noise - unit not boosting or boosting automatically)

Most ventilation systems require electrical controls and accessories to be installed. All controls should be easily accessible and be clearly labelled. For example, ventilation systems boost and SUMMERboost controls should be conveniently located and made obvious to the user. Some units also include automatic functions that may need adjustment such as timer or humidity settings. Always ensure the product handbook instructions have been followed.

8. Not commissioning the system correctly (excessive noise - unit not boosting)

All ventilation systems require on-site commissioning and performance checks to ensure Building Regulations compliance. Commissioning includes setting the unit speeds and using an airflow meter to set the individual room airflow rates to achieve the rates set out by the system designer. It may also include adjusting other settings such as overrun timers and humidity controls. The commissioning engineer should record the installed performance of the ventilation system.

9. Not checking the MVHR unit filters (poor performance)

We recommend that MVHR filters are checked prior to commissioning and handover to the owner as building work produces high levels of contaminants that may enter the ventilation system and block filters. All MVHR units require servicing and filter replacement, the recommended service interval is one year, or less in where ambient pollution levels are higher such as in urban environments.

10. Boxing in the ventilation unit or locating out of normal reach

Ventilation units must remain safely accessible to allow commissioning adjustments, maintenance, repair and end of life replacement. Units must not be ‘boxed in’ and the product handbook includes detailed guidance on access requirements. Any serviceable appliance located in a loft cavity must have safe floor boarding directly from the access hatch to the repair area and provision for adequate lighting to meet with health and safety at work regulations. There are also statutory access requirements where units are installed out of reach.

11 November 2019


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